Embodiments of the present invention relate to a micro focus X-ray tube for a high-resolution X-ray device comprising a housing, an electron beam source for generating an electron beam, and a focusing lens for focusing the electron beam onto a target. Such X-ray tubes are known, for example, for high-resolution computer tomography devices.
Due to advances in detector technology, in computing and in storage capacities as well as the increased resolution of micro focus X-ray tubes, the micro-CT allows the volume reconstruction with a very high spatial resolution (voxel size) up to the sub-micrometer range.
Since the measurement of all the X-ray projections, which are required for a reconstruction with high resolution, takes several hours typically, thermally induced displacements of the sample projections create significant problems on the detector. Although it is known that these displacements are compensated using software-based algorithms, the resolution improvement thus achieved is limited.
The critical component is the X-ray tube, because it is not possible to fix the tube in the focal spot on a thermally insensitive manipulator; it always remains a thermo sensitive (usually metallic) connection over the tubular housing between the focus and the attachment of the tube on the manipulator, which, without further measures leads to the fact that the focus position of the X-ray tube over the duration of measurement moves considerably.
A common measure, to keep the focus position of the x-ray tube over the entire measurement period as constant as possible, consists of heating up the tube to operating temperature and waiting until a thermal equilibrium is reached before the scans are started. However, it takes several hours until the thermal equilibrium is reached because of the considerable mass of the X-ray tube and the associated large heat capacity. Furthermore, the thermal equilibrium is disturbed again with each parameter change of the tube, causing additional significant delays.
The objective of the embodiments of the invention is to provide a micro-focus X-ray tube which allows, in the industrial application, to obtain data in a shorter time with a higher resolution.